Radiation shield circulation system for large liquefied gas storage containers



Feb. 3, 1959 N D. MANN ETAL 2,871,669

. RADIATION SHIELD CIRCULATION SYSTEM FOR LARGE LIQUEFIED GAS STORAGECONTAINERS Filed Dec. 5, 1956 k J INVENTORS DOUGLAS MAN/V ATTORNEY'ZSUnite RADIATION SHIELD CIRCULATION SYSTEM FOR LARGE LIQUEFIED GASSTORAGE CONTAINERS Douglas Mann and John Macinko, Boulder, Colo., as-

slgnors to the United States of America as represented by the Secretaryof the Navy The invention described herein may be manufactured and usedby or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

The invention relates to systems for holding large storage containers atextremely low temperatures.

It is customary in storage containers for liquefied gases, for example,to employ axially concentric shells, with the cooled liquid in the innershell and suitable heat insulation separating the shells. Two shells areusually found adequate for liquefied oxygen or nitrogen but, in the caseof liquefied hydrogen or helium, at least three shells are desirable,the outer shell being at room temperature and the intermediate shell atsome reduced temperature adequate to prevent too rapid heat leak to thelow temperature liquid. In the case of small storage units, the threeshell type is satisfactory where the intermediate shell coolant, such asliquid oxygen, is confined in one section of the heat shield, since theheat path is relatively short and heat is readily conducted to theshield section directly cooled by the refrigerant. In the case of largecontainers, however, this method is inadequate to maintain the containedliquid at the required low temperatures.

- Generally stated, the invention is directed to a cold liquid storagesystem capable of maintaining adequate heat insulation in large or smallsize containers through circulation of a coolant throughout the tankareas under automatic pressure controls.

The objects of the invention, therefore, arev the provision of acirculating cooling system for low temperature maintenance; theprovision of a circulating coolant in storage systems which iscompletely automatic in action; the provision of cooling apparatus forstorage containers which is operative for large or small units; and theprovision of cooling equipment for large containers which may be appliedand utilized at relatively low costs.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. 1 is a vertical section through the liquid gas storage container;

Fig. 2 is a sectional view of the container taken along line 22'of Fig.l;

, Fig. 3 is a schematic view of the storage container in associationwith the control apparatus; and

Fig. 4 is a, detail of the restriction in the lower pipes of the coolantcirculation system to produce abalancing of fiow in the various pipelines. Referring to Fig. 1, the storage unit is shown as ates Pat formedof three cylindrical shells 11, 12 and 13, 11 indicating the containerfor liquefied hydrogen, helium or the like, 12 indicating the containerfor the intermediate coolant and 13 the outer container which isnormally at room temperature. As shown, these shells are spaceduniformly from each other so that, as appears from Fig. 2,

2,871,669 Patented Feb. 3, 1959 axis, numeral 6 indicating a part of theouter shell support, numeral 7 a part of the intermediate shell supportand numeral 8 a part of the inner shell support. The cylindrical wall'of shell 12 is extended, as at 14, beyond the end walls of the shell atboth ends to form annular recesses into which are fitted the two tanks16 and 17 for reception of the coolant liquid such as liquid oxygen.These tanks are similarly shaped, being of cylindrical cross-sectionwith a rounded convexly curved end closure which conforms in shape tothe rounded curvature of the intermediate and outside shells, therebeing provided outlet pipes 18 and 19 at the tank bases, and hydrostaticliquid level gage pipes 20 and 21 and vent pipes 22 and 23,respectively, at the tops of tanks 16 and 17. Inlet pipe 25 with valve26 is provided for liquid supply to container 11 and inlet pipe 27 withvalve 28 for supply of coolant to tank 17. The curved end 30 of tank 16and 31 of tank 17 support in close contact therewith annular manifoldtubes 33 and 34, each tube having a short open pipe, 35 and 36respectively, adjacent to but displaced from the tank bases for passageof liquid to and from the .tank. These manifold tubes constitutestandpipes for reception of coolant from the adjacent tank and deliveryof coolant to the pipe network extending through the annular spacebetween the inner and middle shells 11 and 12 and joining the manifoldtubes. This network includes the straight pipes 37 parallel to thecontainer axis and displaced uniformly in the coolant space 40 about theinner shell 11. Since the flow path from tank to tank is shorter in thebase pipes due to the placement of standpipe inlet-outlet pipes 35 and36 adjacent the tank bases, liquid restriction devices 41, as shown inFig. 4, are placed in these base pipes to equalize the coolant flowthrough all pipes from manifold to manifold. These restrictions may hegraduated in size, with the restrictive orifice smaller in thebottommost pipe and increasing, moving up from the container base, so asto insure uniform flow of coolant through all pipes.

The structure, as above described, illustrates a usable container unitfor low temperature liquid storage. The control mechanism formaintaining the flow of coolant through the pipe lines will now bedescribed.

Referring to Fig. 3 it will appear that level gage pipe 21) from tank 16connects to the outlet pipe 18 through a hydrostatic liquid level gageand level gage pipe 21 from tank 17 connects to outlet pipe 19 throughthe hydrostatic liquid level gage 46. The vent pipes 22 and 23 fromtanks 16 and 17, respectively, are connected together through a pressureequalizing solenoid valve 47. Also, these vent pipes are connected toventing spaces through solenoid valves, pipe 22 through vent valve 48and pipe 23 through vent valve 49. Outlet pipe 18 from tank 16 alsoconnects with pressure actuated electric switch 53 and outlet pipe 19with a similar pressure switch 52, these pressure switches being similarand consisting of a closed chamber 80 having a flexible diaphragm 81therein, two opposed contact switch points 82, 83 connected to a commonterminal 84, a switch arm 35 movable between the contact points and aconnecting rod 36 between the diaphragm and notch arm.

The electric circuit for operating the solenoid valves and electricpressure switches is derived from a power source having terminals 55 and56, terminal 55 having direct connection to the pressure switches 52 and53 and terminal 56 connecting these same switches in parallel through aseries latching relay 58 containing solenoid 59, the solenoidfunctioning on energization to cause step-bystep rotation of a latchingwheel 60. This latter solenoid circuit also includes, in series, atiming switch 61, which functions, on operation of either pressureswitch 52 and 53, to energize solenoid 62 in the pressure equalizingvalve 47, opening the same for a time period of about two to fiveminutes.

The step-by-step latching wheel 60, on rotation by solenoid '59, serves,by'virtue of alternate elevations and depressions 63, 6 4, to move theswitch arm 65'," pivoted at66 between con'ta'cts67 and 68,connectionw-ith contact 67 establishing a circuit through solenoid'70 ofthe solenoid valve 49, closing this valve, valve 43 simultaneouslyopening, and connection with contact fi establishing a circuit throughsolenoid 71 of vent valve 48, closing this valve and simultaneouslyopening vent valve 49.

The operation of the radiation shielding unit is as follows, itbeingassumed that the insideshell 11 hasa supply of liquid hydrogenorhelium, and the tank's'16 and 17 a supply of coolant'such as liquidoxygen in amount sufiicient to fill at least one ofisaid tanks, for

descriptive purposes it beingassumed that the coolantisequally containedin both tanks; It is assumed, also, that the vent'valve 48 is closed,vent valve 49 open' and the pressure equalizing valve 47 closed. Underthese conditions, heat leak to tank 16 causes evaporation ofthecoolant,the gas evolved pressurizing the liquid in the tank and forcing itthrough standpipe manifold 33 intolatching relay 58 and thereby closingvent valve 49andopening vent valve 48. At the same time, timing switch61 opens pressure equalizing valve 47 for a time period of about two tofive minutes, as predetermined for best operation, thus bringing aboutan equalization' of pres sure and levels of the coolant in both tanks.This is necessary in order to insure an adequate supply of coolant intank 17 for subsequent circulation in thepipe-system, and is possiblesince the port opening ofequalization valve 47 is large compared to theport opening of either vent valve. On closure of the pressureequalization valve 47, gas pressure begins to build up in tank 17,forcing coolant through the pipe system back to tank 16, thus providinga continuing coolant shield in the intermediate shell space ill. Thelevel of coolant in tank it: rises due to the inflow from tank 17 untilat about 100 percent capacity level, pressure switch 53 is closed tobring about actuation of latching relay 5% and timing switch 61, thisresulting in closing of vent valve 4-3, opening of vent valve 49 andtimed opening of pressure equalizing switch 47. This cycle of changes iscontinued automatically, thus maintaining an effective low temperatureheat shield in intra-shell space 49, a shield which is normally independent of the size of the storage unit.

As described, the pressure switches close at about l00 percent inflow ofcoolant into the associated tank. However, due to loss of coolant, acondition may arise where the coolant supply is inadequate to fill asingle tank. To meet this situation, the pressure switches are arrangedto make closure contact also at 5 percent of tank supply, so that if the100 percent pressure switch associated with one tank fails to function,the 5 percent pressure switch of the other tank will make contact atpoint 82.

Since the timing, latching, and solenoid switches are of conventionalconstruction, these are not detailed in the drawing or description. Forexample the timing switch may operate on a time clock or similarmovement; the latching switch utilizes the magnetic impulse of solenoid59 to produce'a step movement of wheel 60, and the solenoid switchesfunction to move armatures to actuate valve opening and closing.elements.

Obviously many modifications and variations of the present invention arepossible in'the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A heat-shielded storage container for cold substances comprising astructure of at least three closed shells including an inner shell forholding the cold substance, an outer shell normally at room temperatureonclosing said-inner shell, and an intermediate shell having opposedends interposed between the inner andv outer shells and defining a heatshield, liquid holding tanks placed one at each end of the intermediateshell, coolant pipes connecting said tanks and lying between theintermediate and inner shells, means for supplying cold substances tosaid inner shell and coolant to said tanks, and means for circulatingsaid coolant automatically through said coolant pipes.

2. A heat-shielded storage container for cold sub stances as defined inclaim 1, said coolant circulating means comprising a gas vent pipe foreach of said tanks, a valve in eachofsaid vent pipes, apipeconnectionbetween said vent pipes at the container side of thevent valves, apressure equalizing valve in said vent pipe connection, a pressureelectric switch connected, to each of said tanks movable to closedposition at predetermined pressures in said tanks, a timing switchoperable at closure of either of said pressure switches to close thepressure equalizing valve'for a predetermined time period,

and a latching relay operable atsuccessive closuresof said pressureswitches alternately to close and open one of said vent valves whilesimultaneously opening and closing the other of said vent valves. 7 v

3. A heat-shielded storage container for coldsubstances comprising astructure of'at least three closed shellsincluding an inner shell forholding the cold substance, an outer shell normally at room temperatureenclosing said inner shell, and an intermediate shell interposed betweenthe inner and outer shells and defining a heat shield, liquid-holdingtanks placed one at eachend of the intermediate shell, a standpipepositioned-in each tank and communicating therewith, coolant pipesconnecting the said standpipes and extending between the innerandintermediate shells, means for supplying cold substances to saidinner shell and coolant to said tanks, andmeans forcirculating coolantautomatically through said coolant pipes.

4. A heat-shielded storage container for cold substances as defined inclaim 3, said standpipe including an an nular manifold having a diameterapproximating that of the tank and a port therein positioned adjacentthe base thereof and communicating with the tank interior;

5. The heat-shielded storage container-for cold substances as definedin'claim 4, said coolant pipes extending parallel to the axis of saidinner shell and spaced uniformly thereabout to form an overall heatshield for said inner shell.

6. The heat-shielded storage container for cold substances as'defined inclaim 5, and means inside said coolant pipes which connect the portsection of'said manifolds for balancing liquid'fiow through all of saidcoolant pipes.

7. The heat-shielded storage container for cold substances as defined inclaim 6, said pipe :fiow balancing means comprising orifice restrictionsinside said pipes.

8. In-a'heat-shielded storage container for cold substances including anelongated closed shell -for cold substance storage, coolant tanks ateach end of said shell, coolant pipes between said tanks with said pipesin overlying contiguity with the shell Wall, and ports for supply ofcold substance to said shell and coolant to said tanks, means forobtaining automatic circulation of coolant through saidcoolant' pipescomprising a gasvent pipefor each of said tanks, a valve in each of saidvent pipes, a pipe connection betweensaid vent pipesat the containerside of the vent valves, av pressure equalizing valve in. said vent pipeconnection, a pressure electric switch connected to each of said tanksmovable to closed 5 position at predetermined pressures in said tanks, atiming switch operable at closure of either of said pressure switches toclose the pressure equalizing valve for a predetermined time period, anda latching relay operable at successive closures of said pressureswitches alternate- 1y to close and open one of said vent valves whilesimultaneously opening and closing the other of said vent valves.

References Cited in the file of this patent UNITED STATES PATENTS

